Apparatus for producing reducing elbows



June 12, 1956 c. L. REDMON ETAL 2,750,026

APPARATUS FOR PRODUCING REDUCING ELBOWS Filed May 29 1950 2 Sheets-Sheet 1 I Z a --;I f I H II;

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APPARATUS FOR PRODUCING REDUCING ELBOWS 2 Sheets-Sheet 2 Filed May 29, 1950 IN E TORS m m-,f-.

% Lam TTORNEYS u u 7 1 ll] /v United States Patent APPARATUS FOR PRODUCING REDUCING ELBOWS Charles L. Redmon and Earl T. Sexton, Jr., Louisville,

Ky., assignors, by mesne assignments, to National Cylinder Gas Company, Chicago, 111., a corporation of Delaware Application May 29, 195s, Serial No. 164,952

1 Claim. c1. 205-4 This invention relates to the production of reducing elbows, i. e., curved pipe fittings of progressively changing cross-sectional diameter from one end toward the other, the invention being particularly concerned with the production of such elbows adapted for welding to adjoining pipe fittings or lengths of straight pipe. The invention is concerned with an improved method and also with improved equipment for forming of such reducing elbows.

Among the important objects of the invention is the production of reducing elbows of more uniform shape than has been practicable heretofore, the elbows produced according to the invention having exceptionally smooth internal and external surfaces, substantially free from ridges, wrinkles and other irregularities. Moreover, the elbows produced according to the invention, though of progressively changing wall thickness from one end of the elbow toward the other, are of substantially uniform wall thickness in any cross-sectional plane through the elbow, including the planes at the ends thereof. This simplifies and reduces machining and piping assembly operations.

In considering the nature of the present invention more specifically, it is first mentioned that proposals have heretofore been made to form a reducing elbow by forcing a straight length of pipe into a tapered and curved die cavity, whereby the straight length of pipe is concurrently subjected to a bending operation and a reducing operation. This prior type of operation is subject to serious disadvantages, including the fact that the prior type of operation has a marked tendency to develop wrinkles and irregularities in the reducing elbows formed. In contrast with this prior type of operation, the invention contemplates first forming a curved pipe blank, and then effecting the reducing operation on such curved blank. Thus, according to the invention an elbow of uniform diameter is utilized as a blank for the reducing operation, and this curved blank is placed in a correspondingly shaped portion of a die cavity, from which the blank is forced into a second portion of the die cavity, the second portion being tapered to provide the desired reduction.

In the preferred procedure according to the invention, the reducing elbow is made by first forcing a straight length of pipe over an internal curved and expanding mandrel to provide an elbow of uniform diameter, and thereafter this elbow is utilized as the blank for the final reducing operation. The above-mentioned method of forming the curved blank is, per se, a well known technique and is disclosed for example in Bohling Patent No. 1,353,714, and therefore it need not be described in detail herein. Although in the practice of the present invention, elbows initially formed by other methods may be employed as the curved blanks for the reducing operation, it is especially advantageous to employ the specific preferred two-stage procedure mentioned above since the working of the metal first by being forced over the internal expanding mandrel, and then by being forced into the tapered die cavity produces an elbow which is not only of exceptionally uniform and smooth contour but which is also characterized by exceptional toughness and strength.

There is another and important aspect of the invention to be noted, as follows:

It is contemplated according to the invention that elbows having diiferent amounts of reduction may alternatively be formed with given equipment. This is made possible by virtue of the fact that a curved blank is utilized. Such a curved blank may be forced to a greater or lesser distance into the tapered portion of the die cavity. In this way a given die structure may be utilized in the formation of a plurality of different elbows, each of which would have the same diameter at the large end, but would differ from each other by difference in extent of reduction and thus of diameter at the small end. In the different elbows made in a given die structure, the arcuate extent over which the reduction occurs would, of course, be different, but each style of elbow would nevertheless be of smooth, uniform and symmetrical shape with reference to the central axis of the elbow.

The foregoing capability of the equipment and method of the invention is of great importance because of the relatively great cost of such die structures. This adaptability to the production of elbows having different degrees of reduction constitutes a feature in distinct contrast with prior art techniques where a straight tube is forced into a curved die cavity. In such an arrangement a different die structure would be needed for each individual elbow to be formed, regardless of the amount of reduction.

How the foregoing objects and advantages are attained will appear more fully from the following description referring to the accompanying drawings, in which- Figure 1 is a vertical sectional view through equipment according to the invention, including associated die structure and punch or pusher mechanism;

Figure 2 is a sectional view taken substantially as indicated by the line 22 on Figure 1;

Figure 3 is a top plan view of the die structure, with a portion broken away to illustrate other parts therebelow; and

Figure 4 is a view of a portion of the structure shown in Figure 1, but showing various parts in difierent positions.

In the drawings a sow block 5 is mounted on a press bed, being supported, for example, by a base plate 6. The sow block has a V-shaped cavity formed therein adapted to receive a pair of complementary die parts "i-7 having mating cavities formed therein and configured to provide a die cavity of shape described more fully herebelow. The two parts of the die are adapted to be positioned with respect to each other by means of dowels 8, which dowels provide freedom for movement of the die block parts toward and away from each other.

A guide for the pusher mechanism is associated with the die blocks in the region of the entrance end of the die cavity therein, this guide comprising a cylindrical member 9 with a shouldered portion 10 at the lower end thereof adapted to seat in an annular recess 7a formed in the upper surfaces of the die blocks '7. The guide 9 is removable by a lifting mechanism comprising for example flexible cables 11 supported from the adapter plate 12 which latter is connected to the head of the press mechanism.

The adapter plate 12 also carries the punch member 13 which constitutes the upper element of a series of pusher elements which, as will further appear, comprise a transversely flexible pusher mechanism adapted to enter the curved cavity in the die. The lower end of the punch member 13 is spherically curved as indicated at 14 to interengage with a complementary spherically curved cavity formed in the upper side of the ball 15. Another ball 16 is positioned below the ball and has a spherically curved cavity in its upper side adapted to fit the lower curved surface of the ball 15. The balls 15 and '15 and the lower end of the punch member 13 are interconnected at opposite sides by means of flexible cables 17 so that the balls will be carried upwardly with the punch member 13 when the head of the press is lifted, the flexible cables, however, permitting relative angling of the interconnected elements as the lower ones enter the curved die cavity during downward movement of the press head.

The pusher mechanism still further includes a specially shaped member 18 adapted to engage a work piece placed in the die cavity, as will further appear.

Attention is now called to the configuration of the die cavity in the die blocks 77. In general, the die cavity is curved throughout an arc of substantially 180. The first portion of the die cavity, i. e.-,- the right half thereof, as shown in Figure l, is of uniform diameter and is adapted to receive a blank in the form of a 90 elbow of uniform diameter or cross section, such a blank being indicated at B in Figures 1 and 2. The second portion of the die cavity is of progressively diminishing diameter, the entrance end thereof conforming with the diameter of the first portion of the cavity. The second or tapered portion of the die cavity is symmetrically formed with relation to a projection or continuation of the central axis or center line of the first portion of the cavity, this central axis or center line being indicated by the letter at in Figures 1 and 4.

Attention is also called to the fact that the specially shaped pusher member 18 is shouldered to provide a portion of reduced diameter indicated at 19, which portion is adapted to project into and fit the interior of a blank B inserted in the first portion of the die cavity. In addition, this pusher member, in the region immediately above the shoulder, has a diameter approximately conforming with that of the first portion of the die cavity. The bore in the cylindrical guide 9 also has a corresponding diameter, so that upon insertion of a blank B in the first portion of the die cavity, and placing the pusher member in operating position, the guide 9 may be brought down to the position shown in Figure 1.

With the parts assembled in the manner shown in Figure 1, the head of the press and therefore the punch member 13 is moved downwardly, whereupon the blank B is forced from the first portion of the die cavity into the second or tapered portion thereof, for instance'to the position shown in Figure 4. This effects reduction of the blank and thereby forms a reducing elbow. The flow of metal effected in this way results in a thickening of the metal toward the small end of the elbow, and with the tapered portion of the die cavity shaped as described above with relation to the central axis x, reducing elbows of exceptional regularity and uniformity of shape are produced. While, in Figure 4, the blank is shown as being forced all the way into the tapered portion of the die cavity, it is to be understood that the stroke of the pusher mechanism may be terminated at an early point, thereby forcing the blank only part way into the tapered portion of the die cavity. In this event an elbow is formed having a lesser degree of reduction than where the blank is forced all the way into the die cavity. The extent of the stroke of the pusher mechanism may be limited to a fraction of the full stroke in any suitable way, as by the placement of a stop in the path of some part moving with the punch element 13.

As will be seen from the drawings, the upper surface of the pusher member 13 is cut off at such angle that the point of contact between the ball ldand the member 18 (as viewed in the drawings) lies to the-right of and below the central axis x at-all positions, from that shown in Figure l to that shown in Figure 4. This is of importance in avoiding outward cocking'of the forward end of the member 18 during the time the curved blank is being driven from the first portion of the die cavity to the second portion. It is further of importance in insuring that the projecting lip 26 of the member 18 is retained in snug engagement with the inner curve of the elbow being formed. This projecting lip assists in avoiding distortion or wrinkling of the metal along the inner curve of the elbow during the operation.

When the formation of a piece is completed the press head is lifted, thereby withdrawing the punch member 13 and also the balls 15 and 16. Further lifting of the press head lifts the ball uide 9 away from the die blocks. The elbow and also the pusher member 13 may be removed by forcing them back in the reverse direction from the second portion of the die cavity to the first portion. For convenience, removal may be effected by upward displacement and separation of the die blocks 77. Such upward displacement may be accomplished by means of a plate 21 arranged below the die blocks, this plate having elongated apertures such as shown at 22 in Figure 3 cooperating with headed pins 24, which latter are secured in the die blocks. A member 25 connected with the plate 21 may serve to raise and lower the plate and thus the die blocks.

Separation of the die blocks is conveniently effected by means of tapered tongues 26 (see Figure l) which are formed in the sow block cavity and arranged to project between the inclined surfaces 2727 which are arranged in opposed pairs at the ends of the blocks 77 (see Figures 1 and 3).

When the blocks 7 are raised as above described, the cooperating surfaces of the elements 26 and 27 result in separation of the die blocks, and this in turn results in opening of the die cavity, so that the formed elbow and also the pusher member 18 may readily be removed.

As hereinabove described, it is preferred in the practice of the invention to form the blank B by forcing a section of straight tube over an internal expanding mandrel which is appropriately curved to provide an elbow shaped blank. Such a blank, as shown at B in Figure 1, is then placed in the die cavity as above described, and the blank is forced into the tapered portion of the die cavity to effect the desired reduction. By separating, so to speak, the operations of forming the curved tube and reducing the tube, reducing elbows of exceptional uniformity and smoothness are provided, and this is accomplished with substantial reduction in the force required for any individual operation, as compared with an arrangement in which a straight tube is directly forced into a tapered die cavity.

Various of the arrangements described above contribute to the uniformity of the product obtained according to the invention, including the fact that the pusher mechanism (except for the advance portion of the pusher member 18 which enters the curved blank) is made up of elements which are dimensioned to fit the bore in the guide 9 and also the first portion of the die cavity. The special shape of the member 18 is also of importance in this regard for reasons already noted.

It will be understood that elbows of various degrees of reduction and also of various angular extent and diameter may be formed according to the invention. For most purposes it is preferred to produce elbows, in which case the first portion of the die cavity is of approximately 99 arcuate extent, as is also the second portion.

Reducing elbows may be formed according to the invention from various metals including even quite hard and stain-resistant steels. The operation generally is effected without heating of the blank, but in some cases such heating may be desirable.

We claim:

Equipment for forming reducing elbows from elbowshaped blanks of uniform perimeter, comprising a die structure having a curved cavity therein of length considerably greater than that of the elbow to be produced,

said cavity being curved on a radius approximating that of the central axis of the elbow to be produced and including two curved cavity portions in end-to-end relation, the first portion of the cavity being of substantially uniform perimeter conforming with that of the large end of the elbow to be produced and cross-sectionally adapted to receive and externally support the surface portions of a curved blank adjacent the second portion of the cavity, and the said second portion of the cavity having a perimeter at its entrance end conforming with that of the first portion of the cavity and said second portion of the cavity being of progressively diminishing perimeter toward its other end, and pusher mechanism having a leading head adapted to engage the trailing end of a blank placed in the first portion of the cavity and a force applicator adapted to conform with the curve of the first portion of the cavity, connected to said head and operable to force such blank into the second portion of the cavity.

References Cited in the file of this patent UNITED STATES PATENTS 198,886 Imhof Ian. 1, 1878 Buescher Dec. 8, Dies May 15, Winterhoff Jan. 15, Bohling Sept. 21, Vasselli Mar. 1, Brinkmau Sept. 26, Bergmann June 23, Kenney Nov. 1, Clayton Mar. 21, Kellogg June 12, Flodin Oct. 30, Cornell Mar. 5, Cornell May 21, Singer Mar. 15, Wendel Dec. 19, Stacy Feb. 15, Westin May 1, Whipple Feb. 15,

FOREIGN PATENTS France Jan, 8, 

